This function sets the random number seed for the
rand
operator. If
EXPR
is
omitted, it does
srand(time)
, which is pretty predictable, so
don't use it for security-type things, such as random password generation. Try
something like this instead:[
9
]

one-third of the time.
If you're particularly concerned with this, see the Math::TrulyRandom
module in CPAN.

srand( time() ^ ($$ + ($$ << 15)) );

Of course, you'd need something much more random than that for
serious cryptographic purposes, since it's easy to guess the current time.
Checksumming the compressed output of one or more rapidly changing operating
system status programs is the usual method. For example:

srand (time ^ $$ ^ unpack "%32L*", `ps axww | gzip`);

Do
not
call
srand
multiple times in your program unless you know exactly what you're doing and why
you're doing it. The point of the function is to "seed" the
rand
function so that
rand
can produce a different sequence each time you run
your program. Just do it once at the top of your program, or you won't get
random numbers out of
rand
!